In mobile telecommunications networks, User Equipment (UE) wishing to send data transmit buffer status reports to the base station (eNodeB) indicating the amount of data it has buffered for transmission. In response, the base station allocates appropriate system resources and transmission opportunities to the UE so that it can transmit its data. In the 3GPP, there has been a recent understanding that more detailed buffer status reports should be made to support better QoS-aware scheduling compared with the proposed High-Speed Uplink Packet Access (HSUPA). The inventor has realized that improvements are needed to the way in which the buffer status is reported, to minimize the control signaling overhead needed.
Although for efficiency of understanding for those of skill in the art the invention will be described in detail in the context of a 3G system, the principles of buffer status reporting can be applied to other systems, e.g. other CDMA or wireless in which a mobile device or User Equipment (UE) communicates with one of several other devices (corresponding to eNodeB) with the corresponding elements of the system changed as required.
According to a first aspect, the present invention provides a method of signaling buffer status information from a mobile device to a base station, the method comprising: determining current buffer status information for the mobile device; determining a relationship between the current buffer status information and one or more defined criteria; and sending an absolute buffer status report, indicating the current buffer status, or a relative buffer status report, indicating a change in the buffer status since a previous buffer status report, to the base station in dependence upon the determined relationship.
The buffer status information used in determining the relationship may comprise, for example, the amount of data currently held in the buffer or the rate at which data is being written into the buffer. The reports sent may include the same type of buffer status data or different types of buffer status data as the data used for determining the relationship.
The relationship determined may be a determination that the buffer status information is within certain limits or that it is greater or less than some defined value. For example, if the current buffer status information comprises the change of rate at which data is being written into the buffer since a previous measurement, then the relationship that is determined may be whether the current buffer status information is above or below the defined change of rate.
The relative buffer status report may indicate the change in the amount of data held within the buffer since the previous buffer status report or a change of the rate at which data is being written into the buffer since the previous buffer status report. Preferably, the relative buffer status report indicates a change in the buffer status since the last transmitted absolute buffer status report, as this avoids the propagation of errors that might otherwise result.
The method may also comprise the step of differencing the current buffer status information and the buffer status information corresponding to the last absolute buffer status report, to determine the change in the buffer status since the last transmitted absolute buffer status report.
In one embodiment, the mobile communications device can transmit different types of data at the same time and wherein the buffer status reports include buffer status information for each type of data. Each type of data is preferably associated with a radio bearer group and the buffer status reports include buffer status information for each radio bearer group. This allows the base station to be able to allocate the uplink resources (used for communicating data from the mobile communications device to the base station) based not only on the amount of data in the buffer, but also on the relative priority associated with different traffic types.
The present invention also provides a method of allocating resources to a mobile communications device comprising: storing buffer status information previously received from the mobile communications device and indicating the buffer status within the mobile communications device at a previous time point; receiving from the mobile communications device a relative buffer status report indicating a change in the buffer status within the mobile communications device since a previous buffer status report; using the stored buffer status report and the relative buffer status report to determine a current buffer status within the mobile communications device; and allocating resources to the mobile communications device in dependence upon the determined current buffer status.
The stored buffer status information is preferably an absolute buffer status report indicating the buffer status at the previous time point or it may be buffer status information obtained from such an absolute status report and updated with one or more subsequent relative buffer status reports. Preferably, the method only uses the stored absolute buffer status report and the latest relative buffer status report to determine the current buffer status within the mobile communications device.
In one embodiment, when the base station receives a new absolute buffer status report from the mobile communications device, it replaces the stored absolute buffer status report with the new absolute buffer status report.
The base station will preferably receive such buffer status reports from a number of different mobile devices and will allocate available resources depending on their transmission needs. Where the mobile devices can transmit different types of data having different priorities, the base station preferably allocates resources to one mobile device based on the buffer status reports received from that device as well as in dependence upon the data to be sent from other devices and the priority of that data.
The invention provides, for all methods disclosed, corresponding computer programs or computer program products for execution on corresponding equipment, the equipment itself (user equipment, nodes or components thereof) and methods of updating the equipment.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: